This disclosure relates to a system and a method for buffering (i.e., intermediate storage) of differently cut boards for a wooden structure, in particular a roof truss.
The wooden structure can be a supporting structure of a roof, for example a roof truss (“truss”). Such wooden structures are assembled from differently cut boards. The boards are elongate, in particular straight, and have respectively a longitudinal direction. The truss can be, in particular, a trussed rafter, in particular in the form of a nailed truss or nail plate truss, in which the boards form a supporting structure of compression members and tension members. The totality of the boards designated for such a wooden structure is called a set or board set in the present application. In the case of a truss or similar wooden structures, such a set typically contains approximately one or two dozen cut boards of different length. The length can lie in the range of 20 cm to 6 m. The cross-section of the boards can be, in particular, rectangular. The boards of a set can have different widths and/or thicknesses here.
Trusses and other wooden structures can be prefabricated in production lines. Here, firstly the various boards of a set are cut from large, in particular long, boards. In modern production lines software is used that specifies for a given number of sets, for example eight or twelve sets, the sequence in which the required set elements are to be cut from the large boards which are available. In this way the large boards can be utilized very economically such that as little loss of material as possible occurs. As a consequence, all boards, which are required for the sets, are produced in a production line in a sequence that may change as a function of the available boards to be cut and the numbers and sizes of boards needed for the sets. Often, more boards of a particular cut are repeatedly produced than are required for an individual set. These must therefore be stored intermediately (i.e., buffered), until the respective sets are complete. As soon as a complete set of cut boards is available, the wooden structure, for instance a truss, can then be assembled from this set in a further station of the production line.
Currently in such production lines, a vertically movable rack is used for the intermediate storage of differently cut boards, in the compartments of which rack respectively cut boards for a set are collected lying adjacent to one another. A control unit monitors which set elements, i.e., cut boards, are already present in which rack compartment, and makes provision that only the cut boards which are still missing for the respective set are filled into each rack compartment. As soon as a complete set of boards is contained in such a rack compartment, the set can be removed and delivered to the next production station.
Such vertically adjustable racks are complex, in particular because they are lowered beneath the level of the floor in order to receive the cut boards which are delivered from a conveyor belt.